pkcs15-prkey.c: correctly check for presence of ECC parameters

[hamarituc]

This PR changes the condition to check for special handling of Slovakian Slovenian eID more general. Previous the existence of such parameters was tested if the values are still have their default value. Now existence is tested by parser specific flags. At least it solves #3031. But I don't have access to a Slovakian eID, but it should be checked against such a device.

Mentioning @llogar and @jurajsarinay as they were involved in the implementation of that driver and asking them kindly to check against their hardware.

closes #3031

Checklist

• PKCS#11 module is tested
• Windows minidriver is tested
• macOS tokend is tested

[Jakuje]

lgtm. Checking this works for SKeID would be helpful.

[jurajsarinay]

handling of Slovakian Slovenian eID

This does not affect skeid (RSA only),
might affect the Slovenian eOI by @llogar.

Checking this works for SKeID would be helpful

I have checked my card works. Checking this works for eOI would be helpful.

[llogar]

eOI still works with this PR...

[Jakuje]

Thank you for verification! Then I think we are good to merge this for the upcoming release.